1. Field of the Invention
The present invention relates to user-activated water treatment units and, more particularly to an ultraviolet water treatment unit having a soft start and/or a time delayed shut-off.
2. Description of Related Art
Many UV water treatment systems for use in homes and offices have become available. Generally, these systems are not user-activated. That is, UV radiation in the water UV treatment unit is ongoing whether or not water is being withdrawn. The source of the water may be from a fixed volume container or from a conventional municipal water system. Some of these units have a simple mechanical filter and some may incorporate an activated charcoal filter. The more effective water treatment units incorporate an ultraviolet source to irradiate the water flowing therepast. Other units may include an ozone generator to inject ozone into the water as part of the treatment process.
Yet further sophisticated and effective water treatment units incorporate both an ultraviolet source for irradiating the water flowing therepast and also mechanical filters for removing particulate matter, whether inert or viable. U.S. Pat. Nos. 5,266,215 and 5,540,848 disclose water treatment units that irradiate inflowing water with ultraviolet radiation, transport the irradiated water through a filter and further irradiate the filtered water prior to discharge from the water unit. These two patents are assigned to the present assignee and are incorporated herein by reference.
The introduction of ozone may be incorporated to take advantage of its capability to kill microorganisms and to oxidize matter. An example of such a water treatment unit is provided in U.S. Pat. No. 5,709,799 wherein the water to be treated is ozonated and irradiated with ultraviolet radiation. This patent is owned by the present assignee and is incorporated herein by reference. U.S. Pat. No. 5,540,848 noted above also includes an ozone generator for introducing ozone into the water to be irradiated and filtered.
Traditional ultraviolet water treatment units have a flow through chamber which contains an ultraviolet lamp that is in continuous operation. Several significant detriments exist if an ultraviolet lamp is continuously on even though the water does not flow therepast on a continuing basis. The following is a summary of these detriments. The energy radiated from the ultraviolet lamp tends to heat the surrounding water. Through such heating, the water temperature can rise to a scalding temperature level. If the purpose of the water treatment unit is to provide drinking water for cups and the like, or for other point of use purposes, the heated water is essentially unacceptable. The warm, or even hot water, is conducive to rapid bacterial growth. Thus, the heating effect of the ultraviolet lamp will help to incubate any microorganisms present. Moreover, any bacteria or other microorganisms resident on or in a filter have a protected heated environment within which to grow unchecked. Stagnant water in a container proximate an ultraviolet lamp will tend to stratify. Such stratification may result in water that may not be properly and adequately irradiated with ultraviolet radiation. As the water is heated, its ability to dissolve minerals is increased. Upon an inflow of cold water as a result of use of the water treatment unit, the warm/heated water will suddenly cool. Such cooling may result in release of any dissolved minerals. These released minerals will, over time, coat the ultraviolet lamp, or its protective sheath. Such gradual coating will reduce the amount of radiation transmitted into the water without the user being aware of the resulting reduced efficiency in treating the water. At some point, a health hazard may come into being. The ultraviolet radiation emitted will chemically degrade or alter the transparent envelope surrounding the filament and/or a protective UV transparent sheath. Over time, the envelope and/or sheath will become more and more opaque to ultraviolet radiation. This process is generally referred to as solarization.
The detriments noted above are, by and large, obviated by a use-activated water treatment unit. This is particularly true for water treatment units that are intended for home use or use in an office environment during business hours only. Presently known user-activated water treatment units have two major detriments. The first such detriment is the time necessary for an ultraviolet lamp to achieve full intensity. During this xe2x80x9cramp-upxe2x80x9d period, any water flowing therepast will be irradiated by ultraviolet radiation at less than full intensity. Such reduced intensity of radiation may result in an initial flow of water not being fully or completely irradiated and some viable microorganisms, normally killed by the ultraviolet radiation, may be discharged from the water treatment unit. A filament as a source of radiation, whether in the visible light spectrum or ultraviolet light, in a lamp is are subjected to a rapid temperature increase when energized. The rapid temperature increase causes significant mechanical stresses in the filament. These mechanical stresses will, over a period of time, mechanically weaken the filament and failure of the filament will occur. The number of cycles of energizing and de-energizing the filament are a function of and generally dictate the actual life span of the filament.
A user-activated water treatment unit incorporates an ultraviolet (UV) lamp for irradiating water flowing therepast to kill microorganisms that may be present. Upon energization of the ultraviolet lamp, a soft start circuit gradually increases the current flow through the UV lamp to reduce the rate of heating of the lamp filament and thereby minimize the mechanical stresses incurred by the filament during a ramp up period. To reduce the number of on/off cycles of the ultraviolet lamp a time delay circuit maintains the lamp energized for a set time after an initial water discharge has ceased to permit a close in time subsequent use without turning the lamp off therebetween. Furthermore, the time delay before shut off will irradiate the water remaining after completion of a water discharge to ensure that a subsequent water discharge during the ramp up of the UW lamp period will have been previously filly irradiated to kill microorganisms then present. The soft start circuit and the time delay circuit may be used independently of one another in a water treatment unit.
It is therefore a primary object of the present invention to provide protective measures for enhancing the longevity of an ultraviolet lamp used in a user activated water treatment unit without compromising the killing of any microorganisms present.
Another object of the present invention is to provide a soft start for an ultraviolet lamp used in a user-activated water treatment unit to reduce the stresses imposed upon the lamp filament upon energization.
Still another object of the present invention is to provide a time-delay circuit for extending energization of an ultraviolet lamp in a user activated water treatment unit to reduce the number of cycles of the lamp during a brief interval repeated user activity.
Yet another object of the present invention is to continue to irradiate with ultraviolet radiation water present in a user-activated water treatment unit after water discharge has ceased.
A further object of the present invention is to provide a user activated water treatment unit that will discharge pre-ultraviolet irradiated water upon energization of the unit.
A still further object of the present invention is to provide a method for enhancing the longevity of a filament in an ultraviolet lamp used to irradiate water flowing through a user activated water treatment unit.
A yet further object of the present invention is to provide a method for ensuring that water discharged from a user activated water treatment unit has been pre-irradiated with ultraviolet radiation.
These and other objects of the present invention will become apparent to those skilled in the art as the description thereof proceeds.